The problem remains in Ingo 3.1.1. The problem is very simple - when
adding new rule, which uses not (yet) existing folder, the folder name
is not encoded in utf7imap.

e.g. I want to add new rule, which move emails to folder "ab?". I've
found this in html after entering new mailbox name.
<input id="actionvalue_new" name="actionvalue_new" type="hidden" value="ab?">
but it should be:
<input id="actionvalue_new" name="actionvalue_new" type="hidden"
value="ab&AQ0-">

All existing mailboxes, listed in the dropdown (id="actionvalue"), are
encoded in utf7imap.

So imho there is two options here:
1. Encode mailbox name with javascript right before setting it to
actionvalue_new field.
2. Before saving rule, check weather the mailbox exists. If it
doesn't, convert mailbox name from utf8 to utf7imap before performing
any action further.

If folder name has Lithuanian letters (?????????), and it is chosen
in filter to move to that folder, then another folder is created and
messages are moved to new one. For example folder name is test?, and
when filter rule works, it creates folder named test&AWE-

If folder name has Lithuanian letters (?????????), and it is chosen in
filter to move to that folder, then another folder is created and
messages are moved to new one. For example folder name is test?, and
when filter rule works, it creates folder named test&AWE-